FAOW

[Michael Rothacher]

Lovoltech FAOW

Here's a go:

One watt only.

This has been cooking on the bench all day without issues.

12V switcher PSU and battery tested.

Regular 'ol "big" TO-220 heat sink and clip for cooling. Easiest heat sinking ever.

R2 will need to be adjusted (3-5 ohms) according to the Vgs of your JFETs.

Sweet spot around 9 to 9.5V Vds, .55A Id (ish)

THD <.4% @ 1W, Noise <400uV even with the laptop supply

Want a cute little PCB for easy assembly and mounting?

Is that bench nasty enough for ya?

 

[EUVL]

So how much gain ?


Patrick

 

[Michael Rothacher]

4dB, according to the pic.

Goodnight.

 

[EUVL]

Still like post #47 better.
If you have to use iron anyhow, at least get rid of the output cap.


Patrick

 

[MEPER]

Here's a go:

One watt only.

This has been cooking on the bench all day without issues.

12V switcher PSU and battery tested.

Regular 'ol "big" TO-220 heat sink and clip for cooling. Easiest heat sinking ever.

R2 will need to be adjusted (3-5 ohms) according to the Vgs of your JFETs.

Sweet spot around 9 to 9.5V Vds, .55A Id (ish)


THD <.4% @ 1W, Noise <400uV even with the laptop supply

Want a cute little PCB for easy assembly and mounting?

Is that bench nasty enough for ya?

What is the name of the distortion meter you use to show THD etc.?

 

[Zen Mod]

AP something

 

[MEPER]

Ok.....maybe like this one:
Audio Precision Portable One Plus Audio Analyzer & Generator | eBay


…..now I know the price level of such equipment…….not ready for that yet…..

 

[JPS64]

Referring to post #47, here booster power supply (Pete Millet variant).



Could P1 replaced by CCS?


JP

 

[EUVL]

There are many step-up switchers. Just pick one.
I used LT3751 before, but there are also lower cost solutions.
Just google.

> Could P1 replaced by CCS?

No. And you should replace by fixed resistor once value is determined for 70mA bias.
And if you want both channel to have the same gain, you should match your FETs, so that the source resistor is the same.


Patrick

 

[Michael Rothacher]

No. And you should replace by fixed resistor once value is determined for 70mA bias.
And if you want both channel to have the same gain, you should match your FETs, so that the source resistor is the same.


Patrick

Perfect advice, exactly what should be done.

 

[EUVL]

> here booster power supply (Pete Millet variant).

You referenced your post to Pete Millett.
I have not been able to locate a circuit from Pete that uses LT1170 or other switcher ICs.
Would you care to post a link to your source ?


Thanks,
Patrick

 

[JPS64]

I´ve asking last year Pete to do LTSPICE simulation with WE transformer (easy available in Germany) based on his 10W flyback version. He does this and suggested to use the mentionned WE transformer and to switch to LT1170 (5A) to increase the power. Don´t forget, the supply capability is up to 325V@30W.



10V B+ Flyback Supply


Again many thanks to Pete.


JP

 

[EUVL]

So was it built, or just simulated ?


Patrick

 

[JPS64]

Only simulated.


JP

 

[EUVL]

Good to know.


Patrick

 

[Michael Rothacher]

Lovoltech FAOW

If you need more gain (10dB) e.g. for an iPhone, and permanent adjust-ability, here's an option. Couple more parts tho and .5% THD.

 

[Michael Rothacher]

If my budget allowed, I'd be tempted to try the 1H Hammond 193S. You'd need to take B+ up to 15 volts or so.

 

[Vix]

Hi Michael,
Thank you for the schematic. Its sheer simplicity makes it irresistible
Instead of the Hammond, I guess one can use an appropriate lightbulb or maybe a Microwave oven transformer ...

 

[EUVL]

> Couple more parts tho and .5% THD

Ruins the simplicity.


Patrick

 

[Michael Rothacher]

I don't disagree. That one's more for someone who doesn't want the full monastic experience.